Undervoltage release for circuit breaker



Dec. 20, 1966 5. w. KIESEL ETAL 3,293,577

UNDERVOLTAGE RELEASE FOR CIRCUIT BREAKER Filed Sept. 21, 1965 2Sheets-Sheeti FIG.1

INVENTORS GEORGE W MESH, HENRY E. S. Ownv WM Q w A T TO/FA/E Y Dec. 20,1966 G w. KIESEL ETAL 3,293,577

UNDERVOLTAGE RELEASE FOR CIRCUIT BREAKER Filed Sept. 21, 1965 2Sheets-Sheet 2 INVENTORS GEORGE W. K/ESEL, Haw? Y 5. S. OWEN BY QM 3"HTTO/FNE) United States Patent 3,293,577 UNDERVGLTAGE RELEASE FORCIRCUIT BREAKER George W. Kiesel and Henry E. S. Owen, Unionville,

Conn., assignors to General Electric Company, a corporation of New YorkFiled Sept. 21, 1965, Ser. No. 488,854 Claims. (Cl. 33520) The presentinvention relates to electrical circuit breakers, and more particularly,to electrical circuit breaker assemblies of the type including means forcausing automatic opening in response to predetermined conditions in thecurrent passing therethrough and also means for causing opening inresponse to other electrical conditions such as a change in thecondition of a remote control circuit or a decrease in line voltage.

Electrical circuit breakers commonly have a housing and include manuallyoperable mechanisms for operating contacts thereof between open andclosed circuit positions, and in addition, current responsive means forcausing automatic opening of the contacts upon the occurrence of certainpredetermined current conditions through the circuit breaker. -In acertain number of uses, it is desirable that the circuit breaker includemeans for causing of the opening of the breaker in response to a changein voltage conditions in the circuit, particularly in response to apredetermined drop in the voltage in the circuit. In certain other usesof such circuit breakers, it is also desirable that the circuit breakerinclude means permitting remote operation of the circuit breaker to theopen circuit condition.

It is an object of the present invention to provide a novel, extremelycompact and effective undervoltage tripping device for use inassociation with an electrical circuit breaker.

It is also an object of this invention to provide an undervoltagetripping device for an electrical circuit breaker that has buzzing orchatter control means for the soleniod used therewith.

It is another object of this invention to provide an undervoltagetripping device that allows for overtravel of a resetting lever.

It is a further object of this invention to provide an undervoltagetripping device for use with an electrical circuit breaker which can bereadily converted to provide a remote control tripping device.

It is still another object of this invention to provide an undervoltagetripping device that is adjustable to operate at various percentages ofdesired voltage.

It has been found that the foregoing objects and other advantages can bereadily attained in an undervoltage release device for circuit breakerswhich comprises a support for mounting on an associated circuit breakerand a solenoid mounted on the support. An actuating armature isreciprocally engaged by the solenoid and a tripping plunger is slidablymounted on the support. Compression spring means mounted on the supportengages the tripping plunger for biasing the tripping plunger from alatched position to a tripped position to engage and operate the circuitbreaker trip member of the associated circuit breaker. A latch member ispivotally mounted on the support and is engaged with the actuatingarmature, and the latch member includes a leg portion releasably engagedwith the tripping plunger in the latched position thereof. First tensionspring means which is mounted between the support and the latch memberbiases the latch member in a direction to release the tripping plunger.A resetting lever is pivotally mounted on the support and has a portionengaged with the tripping plunger to effect sliding movement thereof tothe latched position. Second tension spring means is operable by theresetting lever and connects to the latch member or to the actuatingarmature for returning the latch member and the tripping plunger to alatched position when the resetting lever is moved to a predeterminedresetting direction and allows for overtravel of the resetting lever.

In accordance with the general construction, the electrical circuitbreaker used therewith desirably is a multipole molded case type havingat least two elongated chambers therein each containing parts withrelatively movable contacts providing one current path or pole of thecircuit breaker, and current responsive tripping means for causingautomatic opening of all poles simultaneously. The tripping meansincludes a trip member which is movable to cause automatic opening ofthe contacts and which is engaged by the tripping plunger of theundervoltage release device to operate the circuit breaker.

The undervoltage tripping device is installed in a circuit breaker toprovide automatic tripping when loss of power occurs or when there is amajor voltage dip. More particularly, the undervoltage tripping devicehas a solenoid magnet with a moving armature affixed to a springloadedlatch which restrains a spring-biased shaft and plunger. When released,the shaft and plunger move the breaker trip member or bar to trip thebreaker. As long as the voltage connected to the solenoid is normal, thesolenoid magnetic force overcomes the spring force and the plunger doesnot act on the trip bar. If the voltage is removed or dips to apredetermined percentage of rated voltage, the spring force overcomesthe solenoid magnetic force, unlatches the shaft and plunger and tripsthe breaker. Unless the required voltage is restored to the solenoidcoil, the breaker will trip if an attempt is made to close it. Whennormal voltage has been restored, resetting lever is used to move theplunger and lever so that the armature is again magnetically engaged bythe solenoid magnet.

The invention will be more fully understood from the following detaileddescription and its scope will be pointed out in the appended claims.

In the drawings:

FIGURE 1 is a side elevational view of a circuit breaker assemblyincorporating the undervoltage tripping device of this invention withthe case partially broken away to reveal internal construction;

FIGURE 2 is an elevational view to an enlarged scale of a portion of thecircuit breaker assembly of FIGURE 1 showing the undervoltage trippingdevice and a portion of the circuit breaker component partially insection for clarity of illustration;

FIGURE 3 is a top plan view of the undervoltage tripping device ofFIGURE 1 to an enlarged scale showing the device in the on or latchedposition and parts of the circuit breaker in phantom line;

FIGURE 4 is a view similar to FIGURE 3 with the parts shown in thetripped position; and

FIGURE 5 is a persepective view to an enlarged scale of the undervoltagetripping device with parts broken away for clarity of illustration.

Referring now in detail to the attached drawings, the invention is shownin FIGURE 1 as an assembly of the overvoltage release device in anelectric circuit breaker having a generally rectangular insulatingcasing With a base and a cover 12. A pair of relatively movable contacts(not shown) are provided in the base 10 and function as a stationarycontact connected to a line terminal (not shown) mounted on the base It)and a movable contact connected to a load terminal (not shown) on thebase lltl. The movable contact is carried by a contact arm 14 which ispivotally supported in the base 10 by suitable means (not shown) and isrigidly engaged with the contact cross arm 16. In actuality, the circuitbreaker illustrated is a three-pole circuit breaker with three elongatedchambers or current paths or poles, each of which containscurrent-carrying parts and contacts similar to those describedhereinbefore.

An operating mechanism is also mounted in the base 10 for operating thecontact cross arm 16 and the associated contact arms 14 of the otherpole chambers between open and closed circuit positions by means of amanually operable handle member 18. The operating mechanism referred toincludes a normally restrained but releasable member or cradle (notshown), which is adapted to be releasably held by a trip member 20mounted in suitable latch means (not shown) carried by the trip unitgenerally designated by the numeral 22 and adapted to be r leasedthereby upon the occurrence of predetermined current conditions. Anelectric circuit breaker mechanism of the type described is shown, forexample, and more fully described in United States Patent No. 3,155,803,granted on November 3, 1964, to Kline and Powell, and assigned to thesame assignee as the present invention. The trip unit 22 includes aseparate box-like insulating enclosure and may be of any suitable typehaving a trip member 20 which is movable to cause the breaker to trip. Atrip unit of the type described is shown in United States Patent No.3,162,739 granted December 24, 1964, to Kline and Powell and assigned tothe same assignee as the present invention.

For the purpose of initiating trip operation of the trip unit 22 uponthe occurrence of a predetermined decrease in voltage in a selectedcircuit, for instance, as the circuit provides current through thestationary and moving contact described above, an undervoltage trippingdevice is provided as shown and designated generally by the numeral 24.

Referring particularly to FIGURES 2 through 5, the undervoltage trippingdevice 24 comprises a generally flat sheet metal support frame orsupport generally designated by the numeral 26 and having bentover endor side wall portions 28, 30 and 32. The side wall portion 32 abutsagainst a wall portion 23 of the trip unit 22. A solenoid 34 is rigidlymounted on the frame 26 by suitable means and has an actuating armature35 reciprocally disposed in the core thereof.

A tripping plunger, generally designated by the numeral 36, is slidablysupported in suitable apertures (not shown) of the sidewall portions 28and 30 and is adjustable in length by means of a threaded portion 38 ofreduced cross section which is threadably received within the tripengaging portion 40. The reduced cross-section of the threaded portion38 provides a notch with a shoulder portion 39 on the tripping plunger36 for a purpose to be described hereinafter. To permitfacile adjustmentwith a screwdriver, a slot 37 is provided in one end of the trippingplunger 36. Thus, the tripping plunger 36 is adjustable in length toobtain proper and effective engagement with the trip unit 22.

The tripping plunger 36 is disposed within a helical compression spring42 which is mounted between the side wall portion 28 and a washer 44providing a radially outwardly extending shoulder on the trippingplunger 36 and biases the tripping plunger 36 toward the trip unit 22.The trip engaging portion 46 extends through side wall 30 and engages aspring biased tripping rod 46 slidably supported in an aperture 45 inthe wall 23 of the trip unit 22 and biased toward the trip engagingportion 40 by spring 47. The piston 46 extends through the wall 23 ofthe trip unit 22 and engages the trip member 23. Thus, the trippingplunger 36 is biased by compression spring 42 toward engagement withtripping rod 46 which is slidable to engage and move trip member 24) totrip the circuit breaker.

For the purpose of releasably holding the tripping plunger 36 againstmovement to the left due to the biasing pressure of the compressionspring 42, a latch member 48 is pivotably supported on a reduced endportion 50 of the post 52. One end of the latch member 48 is slidablyconnected to the actuating armature 35 of the solenoid 34 by means of apin 56 which is disposed in an elongated aperture (not shown) in thelatch member 43 to permit relative sliding movement therebetween. Thelatch member 48 is constantly biased for rotation in a counterclockwisedirection as illustrated in FIGURE 3 so that the armature 54 isconstantly subjected to a force tending to move it away from magneticengagement with solenoid 34, by means of the tension spring 58 which ismounted between the other end of the latch member 48 and the side wallportion 23. A screw 60 having the same pitch as the spring 58 passesthrough an aperture (not shown) in the side wall portion 28 and threadsinternally into the spring 58. The tension or biasing force on the latchmember 48 may be adjusted by turning the screw 64) whereby a portion ofthe spring 58 may be released or taken up by the threaded shank of thescrew 60. Thus, the force biasing the armature 35 away from the solenoid34 may be adjusted by means of screw 60 so that the armature 35 is movedfrom magnetic engagement with the solenoid 34 at the predeterminedpercentage of rated voltage. Also, adjusting the force of spring 58 doesnot affect the spring force biasing the tripping plunger 36. By reasonof the latch construction as described, the force required by thesolenoid 34 to hold the armature 35 against the force of spring 58 issubstantially less than the force that would be required by a solenoidto hold an armature against the force of the spring 42.

The tripping plunger 36 is held in the latched position by a leg portion62 extending normally to the latch member 43 for engagement with theshoulder portion 39 formed by the reduced cross section of the threadedportion 38 on the tripping plunger 36 when the latch member 48 is heldin the latched position by the engagement of the armature 35 by thesolenoid 34. Thus, when the sole noid 34 magnetically engages thearmature 54 and holds the latch member 48 in the latched position, asillustrated in FIGURE 3, the leg 62 engages the shoulder portion 39 ofthe tripping plunger 36 so that the trip engaging portion 40 isrestrained from engagement with the tripping rod 46 of the trip unit 22.When the voltage energizing the solenoid 34 falls below thepredetermined percentage of rated voltage, the armature 35 is releasedand the latch 48 is rotated by the force of the tension spring 58 sothat the leg portion 62 is moved from engagement with shoulder 39 andtripping plunger 36 is moved into engagement with tripping rod 46 whichin turn engages trip member 20, thereby tripping the circuit breaker.

In order to reset the undervoltage tripping device 24, a resetting leveris mounted on a bracket 71 of the frame 26 by means of a pivot pin 72,and extends generally normally to the tripping plunger 36. A leg portion74 of the tripping lever '70 engages the shoulder portion 44 on thetripping plunger 36, and the undervoltage tripping device 24 may bereset from the tripped position shown in FIGURE 4 to the latchedposition shown in FIGURE 3 by rotating the resetting lever 70 in aclockwise direction as viewed in FIGURE 2 so that the leg portion 74engages the shoulder 44 and moves the tripping plunger 36 to the latchedposition. A second tension spring 76 in the form of a helical coil isconnected between the leg portion 74 and an aperture 78 in the latch 48so that, as the resetting lever 76 is rotated, the spring 76 biases thelatch member 48 and the armature 54 into the latch position. The spring76 also allows for overtravel of the resetting lever 7 after thearmature 35 has been engaged by solenoid 34. If normal voltage has beenrestored to the solenoid 34, the armature 35 will be held by thesolenoid and the latch member 48 will be retained in the latchedposition by engagement of the leg portion 62 thereof with the shoulderportion 39 so that the tripping plunger 35 is restrained from moving tothe tripped position.

The solenoid 34 is provided with buzz or chatter reducing means similarto that described in Patent No. 3,117,257 issued to Richard S. Stone onJanuary 7, 1964. The drop-out voltage of the solenoid may be set to thedesired percentage of rated voltage by the adjusting screw 60 andbuzzing or chattering in the solenoid 34 at the selected voltage may bereduced by rotating the buzz control member 36. Thus, an undervoltagetripping device is provided that may be set to operate at a highpercentage of rated voltage where buzzing and chattering frequentlyoccur, and which may be easily and tconveniently removed by adjustingthe buzz control member 80. The reference voltage is supplied to thesolenoid 34 by means of the wires 82.

In FIGURES 1, 3 and 5 the parts are shown in the position which theyoccupy during normal operation of the circuit breaker. In this position,the tripping plunger 36 is held in retracted position when the solenoid34 is energized by a reference voltage, thereby holding the latch member48 in the latched position against the bias of the spring 58. In thisposition, the leg portion 62 engages the shoulder 39 of the trippingplunger 36, thereby restraining the tripping plunger 36 from movementinwardly toward the trip unit 22. If the voltage applied to the solenoid3 decreases a predetermined amount, the field acting upon the armature35 will be reduced sufliciently so that it will be moved outwardly ofthe solenoid 34 by the action of the spring 58. As this occurs, thelatch member 48 rotates and the leg portion 62 becomes disengaged fromthe shoulder 39, permitting the tripping plunger 36 to be moved inwardlyby the compression spring 42 and to engage the tripping rod 46 whichmoves inwardly against the bias of spring 47 and actuates the tripmember 2%, thereby initiating tripping action of the circuit breaker.

After the breaker has been tripped due to actuation of the undervoltagetripping device 24, the circuit breaker may be reset by movement of thecontact arm 14 by the action of the operating mechanism actuated byhandle 18 being moved to the off position. The contact arm 14 rotates ina counterclockwise direction when moving to the off position asillustrated in phantom line in FIGURE 2, and as the contact arm 14 isrotated, the contact cross arm 16 engages the resetting lever 70 androtates it in a clockwise direction to the position illustrated inphantom line in FIGURE 2. As the resetting lever 70 is rotated, thetension spring 76 rotates the latch member 48, and the armature 35 ismoved into engagement with the solenoid 34. If the reference voltageapplied to solenoid 34 is of proper value, the armature 35 will then beheld within the solenoid 35 and the latch member 48 will retain thetripping plunger 36 in the latched position ready for subsequentoperation, and the handle 18 of the breaker may be turned to the onposition.

If the handle 18 is moved to the on position before the voltage appliedto solenoid 34 has returned to the preset value, the tripping plunger 36will trip the breaker in the manner described above when the contactcross arm 16 and resetting lever 79 move to the on position illustratedin solid line in FIGURE 2. This occurs because neither the latch member48 nor the resetting lever 70 will restrain the tripping plunger 36' inthe latched position.

In accordance with this invention, the circuit breaker and undervoltagetrip device 24 are both designed to cooperate in such a way that thetrip device can be securely mounted within the insulating casing of thecircuit breaker with a minimum of fastening elements.

In accordance with another aspect of this invention, the parts may bereadily adapted to operate as a remote trip device, rather than as anundervoltage trip device. In the undervoltage trip device, the parts arenormally biased toward tripping condition but are restrained fromcausing tripping by the solenoid which is normally energized, and afailure in voltage in the solenoid therefore permits tripping to occurby spring action. In the remote trip device, the parts are normally in alatched condition and are moved temporarily to a tripped condition bymeans of the solenoid armature or plunger action.

This remote trip form of the invention has parts corresponding to theparts previously described with the excention that the solenoid 34 hasan armature plunger which is normally positioned in an unattracted orouter position and operates a rod connected to a latch member similar tothe latch member 48. A tension spring similar to tension spring 58 isengaged with the latch, in this case between the pivot of the latchmember and the rod. The tension spring in this form therefore tends tohold the latch member in its latched condition. When the solenoid isenergized, however, the armature is pulled into the coil moving the pushrod and rotating the latch member against the pull of the tensionspring. This releases the tripping plunger to the tripped position inthe same manner as previously described. As the contact arm moves towardthe open position, the contact cross arm engages the resetting lever andcauses resetting of the latch member 48, and movement of the trippingplunger to the original position in the manner similar to that describedfor the undervoltage tripping device.

Accordingly, there is provided by this invention an undervoltage tripdevice which is compact and effective, has adjustable parts, and whichcan be readily mounted in a circuit breaker. The tripping plunger may beadjusted to be engaged properly with the tripping unit and the drop-outvoltage may be set at the desired percentage of rated voltage and thesolenoid adjusted to reduce buzzing and chattering. A coil springbetween the latch and resetting lever provides for overtravel of thelever. Moreover, the specifically described undervoltage trip device canbe readily converted to a shunt-trip device with similar operation andadvantages.

While we have disclosed only certain embodiments of the invention, itwill be readily appreciated that many modifications thereof may be made.We, therefore, intend by the appended claims to cover all suchmodifications as fall within the true spirit and scope of the invention.

What we claim is new and desire to secure by Letters Patent of theUnited States is:

1. An automatic tripping device for circuit breakers comprising:

(a) a support for mounting on an associated circuit breaker;

(b) a solenoid mounted on said support;

(c) an actuating armature reciprocally engaged by said solenoid;

(d) a tripping plunger slidably mounted on said support;

(e) a compression spring means mounted on said support and engaging saidtripping plunger for biasing said tripping plunger from a latchedposition to a tripped position to engage and operate a circuit breakertrip member of the associated circuit breaker;

(f) a latch member pivotally mounted on said support and engaged withsaid actuating armature, said latch member including a leg portionreleasably engageable with said tripping plunger in the latched positionthereof;

(g) first tension spring means mounted between said support and saidlatch member for biasing said latch member in a direction to releasesaid tripping plunger;

(h) a resetting lever pivotally mounted on said support and having aportion engaged with said tripping plunger to effect sliding movementthereof to the latched position; and

(i) second tension spring means operable by said resetting lever andconnected to one of said latch member and actuating armature forreturning said latch member and said tripping plunger to a latchedposition when said resetting lever is moved'to a predetermined resettingdirection and allowing for overtravel of said resetting lever.

2. The automatic tripping device of claim 1 wherein said solenoidincludes means to reduce buzzing and chattering when actuated byalternating current.

3. The automatic tripping device of claim -1 wherein said first tensionSpring means is adjustable for changing the force applied to said latch.

4. The automatic tripping device of claim 1 wherein said trippingplunger has a shoulder portion engaged with said compression spring andsaid resetting lever.

5. The automatic tripping device of claim 1 wherein said trippingplunger is adjustable in length to increase and decrease its length forengagement with the trip member of the associated circuit breaker.

6. The automatic tripping device of claim 1 wherein said second tensionspring means is connected between said resetting lever and said latchmember.

7. The automatic tripping device of claim v1 wherein said second tensionspring means is a helical spring.

8. For use with an associated electric circuit breaker including atleast one pair of relatively movable contacts, operating mechanism foroperating said movable contacts between said open and closed circuitpositions and trip means including a trip member movable to causeautomatic opening of said contacts, an automatic tripping devicecomprising:

(a) a support for mounting on the associated circuit breaker;

(b) a solenoid mounted on said support;

() an actuating armature reciprocally engaged by said solenoid;

(d) a tripping plunger slidably mounted on said support;

(e) compression spring means around said tripping plunger and mountedbetween said support and a shoulder portion of said tripping plunger forbiasing said tripping plunger from a latched position to a trippedposition to engage and operate the circuit breaker trip member of theassociated circuit break- (f) a latch member pivotally mounted on saidsupport and slidably engaged with said actuating armature, said latchmember including a leg portion releasably engageable with said trippingplunger in the latched position thereof;

(g) first tension spring means mounted between said support and saidlatch member for biasing said latch member in a releasing direction torelease said tripping plunger, said solenoid when energized by currentpassing therethrough serving to hold said actuating armature inretracted position to retain said latch member in latching positionagainst the biasing force of said first tension spring means;

(h) a resetting lever pivotally mounted on said support and having aportion engaged with said shoulder portion of said tripping plunger toeffect sliding movement thereof to the latched position; and

(i) second tension spring means between said resetting lever and saidlatch member for returning said tripping plunger and said latch memberto latched position when said resetting lever is moved to apredetermined resetting direction and allowing for overtravel of saidresetting lever.

9. The automatic tripping device of claim 8 wherein said first tensionspring means is adjustable for changing the force applied to said latch.

lit. The automatic tripping device of claim 8 wherein said trippingplunger is adjustable in length to increase and decrease its length forengagement with the trip member of the associated circuit breaker.

11. The automatic tripping device of claim 8 wherein said solenoidincludes means to reduce buzzing and chattering when actuated byalternating current.

12. An undervoltage release device for circuit breakers comprising:

(a) a support mounted on an associated circuit break- (b) a solenoidmounted on said support;

(c) an actuating armature reciprocally engaged by said solenoid;

(d) a tripping plunger slidably mounted on said side wall portion ofsaid support, said tripping plunger being adjustable in length forengagement with and to operate a trip member of the associated circuitbreaker;

(e) compression spring means around said tripping plunger and mountedbetween said support and a shoulder portion of said tripping plunger forbiasing said tripping plunger from a latched position to a trippedposition to engage and operate the trip member of the associated circuitbreaker;

(f) a latch member pivotally mounted on said support and slidablyengaged with said actuating armature, said latch member including a legportion releasably engageable with said tripping plunger in the latchedposition thereof;

(g) first tension spring means mounted between said support and saidlatch member for biasing said latch member in releasing direction torelease said tripping plunger, said first tension spring means beingadjustable for changing the force applied to said latch, said solenoidwhen energized by current passing therethrough serving to hold saidactuating armature in retracted position to retain said latch member inlatching position against the biasing force of said first tension springmeans;

(h) a resetting lever pivotally mounted on said support and having aportion engaged with said shoulder of said tripping plunger to effectsliding movement thereof to the latched position; and

(i) second tension spring means between said resetting lever and saidlatch member for returning said lever and said tripping plunger to alatch position when said resetting lever is moved to a predeterminedresetting direction and allowing for overtravel of said resetting lever.

13. The undervoltage release device of claim 12 wherein said solenoidincludes means to reduce buzzing and chattering when actuated byalternating current.

14. An undervoltage release device for circuit breakers comprising:

(a) a support having bottom and side wall portions mounted on anassociated circuit breaker;

(b) a solenoid mounted on said support having means to reduce buzzingand chattering when actuated with alternating current;

(c) an actuating armature reciprocally engaged in said solenoid;

(d) a tripping plunger slidably mounted on said side wall portions ofsaid support having a first and second shoulder portion, said trippingplunger being adjustable in length for engagement with and to operate atrip member of the associated circuit breaker;

(e) compression spring means around said tripping plunger and mountedbetween one of said side wall portions of said support and said firstshoulder portion of tripping plunger for biasing said tripping plungerinto a tripping direction to engage and operate the trip member of theassociated circuit breaker;

( f) a latch member pivotally mounted on said support and slidablyengaged with said actuating armature, said latch member including a legportion releasably engageable with said second shoulder portion of saidtripping plunger in the latched position thereof;

(g) first tension spring means mounted between one of said side wallportions of said support and one end of said latch member for biasingsaid latch member in releasing direction to release said trippingplunger, said first tension spring means being adjustable for changingthe force applied to said latch, said solenoid when energized by currentpassing therethrough serving to hold said actuating armature inretracted position to retain said latch member in latching positionagainst the biasing force of said first tension spring means;

(h) a resetting lever pivotally mounted on said support and having a legportion engaging said first shoulder portion on said tripping plunger toeffect sliding movement thereof to the latched position, said leverextending generally normal to said tripping plunger; and

(i) second tension spring means between said latch member and saidresetting lever for returning said lever and said tripping plunger tolatched position when said resetting lever is moved to a predeterminedresetting direction and allowing for overtravel of said resetting lcver.

15. An electrical circuit breaker assembly comprising:

(A) an electrical circuit breaker including:

(1) a housing,

(2) at least one pair of relatively movable contacts in said housing,

(3) operating means for operating said contacts between open and closedcircuit position, and

(4) trip means including a trip member movable to cause automaticopening of said contacts; and

(B) an undervoltage release device for said circuit breaker comprising:

(1) a support mounted on said circuit breaker housing,

(2) a solenoid mounted on said support,

(3) an actuating armature reciprocally engaged by said solenoid,

(4) a tripping plunger slidably mounted on said support,

(5) compression spring means mounted on said support and engaging saidtripping plunger for biasing said tripping plunger from a latchedposition to a tripped position to engage and operate said circuitbreaker trip member of said circuit breaker,

(6) a latch member pivotably mounted on said support and engaged withsaid actuating armature, said latch member including a leg portionreleasably engageable with said tripping plunger in the latched positionthereof,

(7) first tension spring means mounted between said support and saidlate-h member for biasing said latch member in a direction to releasesaid tripping plunger,

(8) a resetting lever pivotably mounted on said support and having aportion engaged with said tripping plunger to effect sliding movementthereof to the latched position, and

(9) second tension spring means operable by said resetting lever andconnected to one of said latch member and actuating armature forreturning said latch member and said tripping plunger to a latchedposition when said resetting lever is moved to a predetermined resettingdirection and allowing for overtravel of said resetting lever.

16. The circuit breaker assembly of claim 15 wherein said solenoidincludes means to reduce buzzing and chattering when actuated byalternating current.

17. The circuit breaker assembly of claim 15 wherein said first tensionspring means is adjustable for changing the force applied to said latch.

18. The circuit breaker assembly of claim 15 wherein said trippingplunger has a shoulder portion engaged with said compression spring andsaid resetting lever.

19. An electrical circuit breaker assembly comprising: (A) an electricalcircuit breaker including:

(1) a housing,

(2) at least one pair of relatively movable contacts in said housing,

(3) operating means for operating said contacts between open and closedcircuit position, and

(4) trip means including a trip member movable to cause automaticopening of said contacts; and

(B) an undervoltage release device for said circuit breaker comprising:

(1) a support mounted on said circuit breaker hous- (2) a solenoidmounted on said support,

(3) An actuating armature reciprocally engaged by said solenoid,

(4) a tripping plunger slidably mounted on said sup- (5) compressionspring means around said tripping plunger and mounted between saidsupport and a shoulder portion of said tripping plunger for biasing saidtripping plunger from a latched position to a tripped position to engageand operate said circuit breaker trip member of said circuit breaker,

( 6) a latch member pivotally mounted on said support and slidablyengaged with said actuating armature, said latch member including a legportion releasabl y engageable with said tripping plunger in the latchedposition thereof,

(7) first tension spring means mounted between said support and saidlatch member for biasing said latch member in a releasing direction torelease said tripping plunger, said solenoid when energized by currentpassing therethrough serving to hold said actuating armature inretracted position to retain said latch member in latching positionagainst the biasing force of said first tension spring means,

(8) a resetting lever pivotably mounted on said support and having aportion engaged with said shoulder portion of said tripping plunger toeffect sliding movement thereof to the latched position, and

(9) second tension spring means between said resetting lever and saidlatch member forreturning said tripping plunger and said latch member tolatched position when said resetting lever is moved to a predeterminedresetting direction and allowing for over-travel of said resettinglever.

20. An automatic tripping device for circuit breakers comprising:

(a) a support for mounting on an associated circuit breaker;

(b) a solenoid mounted on said support;

(c) an actuating armature reciprocally engaged by said solenoid;

(d) a tripping plunger slidably mounted on said support, said trippingplunger being adjustable in length for engagement with and to operate atrip member of the associated circuit breaker;

(e) a compression spring means mounted on said support and engaging saidtripping plunger for biasing said tripping plunger from a latchedposition to a tripped position to engage and operate a circuit 11 12breaker trip member of the associated circuit (h) a resetting leverpivotally mounted on said supbreaker; port and having a portion engagedwith said tripping a latch member Pivotally mounted 011 said P- plungerto efiect sliding movement thereof to the port and engaged with saidactuating armature, s aid latchgd position latch member including a legportion releasably 5 engageable With said tripping plunger in thelatched NO references cited position thereof; (a) adjustable tensionSpring means mounted between BERNARD A. GILHEANY, Primary Examiner.

said support and said latch member for biasing said latch; and 10 R. N.ENVALL, JR., Assistant Exammer.

20. AN AUTOMATIC TRIPPING DEVICE FOR CIRCUIT BREAKERS COMPRISING: (A) ASUPPORT FOR MOUNTING ON AN ASSOCIATED CIRCUIT BREAKER; (B) A SOLENOIDMOUNTED ON SAID SUPPORT; (C) AN ACTUATING ARMATURE RECIPROCALLY ENGAGEDBY SAID SOLENOID; (D) A TRIPPING PLUNGER SLIDABLY MOUNTED ON SAIDSUPPORT, SAID TRIPPING PLUNGER BEING ADJUSTABLE IN LENGTH FOR ENGAGEMENTWITH AND TO OPERATE A TRIP MEMBER OF THE ASSOCIATED CIRCUIT BREAKER; (E)A COMPRESSION SPRING MEANS MOUNTED ON SAID SUPPORT AND ENGAGING SAIDTRIPPING PLUNGER FOR BIASING SAID TRIPPING PLUNGER FROM A LATCHEDPOSITION TO A TRIPPED POSITION TO ENGAGE AND OPERATE A CIRCUIT BREAKERTRIP MEMBER OF THE ASSOCIATED CIRCUIT BREAKER; (F) A LATCH MEMBERPIVOTALLY MOUNTED ON SAID SUPPORT AND ENGAGED WITH SAID ACTUATINGARMATURE, SAID LATCH MEMBER INCLUDING A LEG PORTION RELEASABLYENGAGEABLE WITH SAID TRIPPING PLUNGER IN THE LATCHED POSITION THEREOF;(G) ADJUSTABLE TENSION SPRING MEANS MOUNTED BETWEEN SAID SUPPORT ANDSAID LATCH MEMBER FOR BIASING SAID LATCH; AND (H) A RESETTING LEVERPIVOTALLY MOUNTED ON SAID SUPPORT AND HAVING A PORTION ENGAGED WITH SAIDTRIPPING PLUNGER TO EFFECT SLIDING MOVEMENT THEREOF TO THE LATCHEDPOSITION.